Cycles outline objects
Consider using freestyle.  Please search freestyle. There are many video tutorials on freestyle. Then show your work.  You may want to use freestyle with Blender Render to reduce time during your learning experience.  You can use the compositor to combine lines with a regular rendered image.

Also you can use the compositor put lines around objects all by itself.  The line can be a glow.  This is possible because Blender can reveal contrast between a transparent background or object id and the surrounding image.